Friends and Enemies

1. Hop aphid (Phorodon humuli)The most important pest of the hop plant which is used as a summer host. In May/June the plant is colonized by flying aphids the so-called winged aphids. These aphids produce asexual wingless larvae which become adults after shedding their skin 4 times (in about 5 days) and are consequently capable of reproducing. One aphid has about 25 descendants. In the autumn they change to a winter host (damsons, plums, sloes). Hop aphids are light green with dark stripes and damage the hops first and foremost by extracting the sap (phloem sucker). Caused by their metabolism they produce a sugary liquid, the honey dew. This is colonized by black fungi.

The hop aphid breeds very rapidly so that in a short space of time dense colonies can be found on the hops. The plants are considerably damaged by the sucking activity on the flowers, cone buds and foliage. Phorodon humuli is also a carrier of the hop mosaic virus.

2. Common spider mite(Tetranychus urtica)The common spider mite, also known as "red spider", causes damage by sucking. Through this the upper sursface of the leaves turn yellowy to reddish brown. Reproduction Is by eggs. Dry-warm weather is beneficial for their development.

The overwintering of the common spider mite on hops occurs via yellow-orange, fertilized winter females preferably on dead leaves or laterals. In the spring these "winter females" lay glassy to slightly yellowy eggs about 0.13 mm In size preferably on the underside of the leaves.

The attacks begin on the lower leaves of the plant. The population of spider mites wanders upwards very rapidly. According to the respective variety more or less strongly developed yellow patches appear on the leaves.

3. Minor pestsBesides hop aphid and the common spider mite numerous other insects can be found on the hops, among them a few can be classed as "minor pests". These insects do in fact live on and from the hops, but at the same time do not generally cause any damage or any damage worth mentioning.

Some of the species may only result in economical losses for hops in exceptional years or under special site conditions.